The invention relates to a medical device for carrying out at least one medical function and to a base part for use in such a medical device. Such medical devices and base parts are used, in particular, in the field of medical diagnostics and/or therapeutics. By way of example, the medical device may be embodied as a long-term sensor and comprise at least one sensor element, which can be inserted into a body tissue of the user, and a control part, which is connected to this sensor element and applied to a body surface of the user, in order to acquire, qualitatively and/or quantitatively, one or more analytes in a bodily fluid of the user, for example over a period of a number of days, weeks or months. Alternatively, or in addition thereto, the medical device can also be designed for therapeutic purposes and can for example be embodied as a medication device. Hence, the medical device may, for example, comprise at least one cannula, which can be inserted into a body tissue of the user, and at least one control part, which is connected to this cannula and arranged on the body surface, for example with at least one medication pump, for example in order to administer one or more medicaments into the body tissue over a relatively long period of time. Various other embodiments are possible.
Numerous medical devices with diagnostic, therapeutic or surgical functions are known. In particular, monitoring and/or influencing certain body functions, preferably monitoring one or more concentrations of certain analytes, plays a substantial role in preventing and treating various diseases such as diabetes. Without restricting further possible applications, exemplary embodiments are described below substantially with reference to blood-glucose monitoring, more particularly with reference to continuous, long-term blood-glucose monitoring over a number of hours, days, weeks or even months. However, in principle these teachings can be transferred to other types of analyte monitoring and/or to monitoring other types of body functions, and also to different fields in medicine. In particular, the invention can also be applied to medical therapeutics, for example to medication pumps such as insulin pumps.
Continuous measurements are becoming ever more established in addition to so-called point measurements of one or more analytes, in which a sample of a bodily fluid is taken from a user in a targeted fashion. Thus, for example, a continuous glucose measurement in the interstitium (also referred to as continuous monitoring [CM]) has been established in the recent past as an important method for managing, monitoring and controlling a diabetes state, for example. In general, this continuous monitoring is initially restricted to type I diabetics, i.e. diabetics who usually also wear an insulin pump. However, other user types are gradually being considered as well. By now, use is generally made of directly implanted electrochemical sensors, which are often also referred to as needle-type sensors (NTS). Here, the active sensor region is brought directly to the measurement location, which is generally arranged in the interstitial tissue and converts glucose into electric charges, for example by using an enzyme (e.g. glucose oxidase, GOD), which charges are proportional to the glucose concentration and can be used as a measurement variable. Examples of such transcutaneous measurement systems are described in U.S. Pat. No. 6,360,888 or in U.S. Publication No. 2008/0242962 A1.
Hence, current continuous monitoring systems are generally transcutaneous systems. In general, this means that the actual sensor is arranged at least partly below the skin of the user. However, a control part of the system, which is also referred to as a patch, is generally situated outside of the body of the user, i.e. outside of the human or animal body. In the process, the sensor is generally applied by means of insertion instruments and is inserted into the body tissue through a skin surface, which is likewise described in U.S. Pat. No. 6,360,888 in an exemplary fashion. Other types of insertion instruments are also known. In general, a sensor is worn for a period of approximately one week; however, longer periods of wear, for example up to one or more months, are also possible. Thereafter, the sensitivity of the sensor generally drops off as a result of influences such as, for example, enzymes being used up and/or the sensor becoming encapsulated in the body, and hence the sensor can be expected to fail. Increasing the length of the period of wear is an area of active research. However, this means that the sensor, and optionally components such as an insertion needle directly connected thereto, should be embodied as replaceable elements. Accordingly, the sensor and, in general, further replaceable components of the device constitute a so-called disposable. However, an actuation unit of the control part, which comprises expensive components of the same (such as high-resistance amplifier input stages and/or potentiostats and/or similar active elements), is generally reused and so the device often comprises at least one reusable component.
In the case of implantable sensors, the disposable generally comprises a so-called body mount, which can be affixed to a skin surface of the user. By way of example, the body mount generally contains a base part and at least one plaster in order to affix this base part onto the skin surface. The reusable, which may contain the essential parts of actuation and/or evaluation electronics for measuring the analyte concentration, is then connected to this body mount, which generally also carries the insertable sensor. However, components such as at least one battery can be arranged in the body mount itself, and so when a body mount is replaced, and a new body mount and the reusable are assembled, the device is at the same time also embodied with a new source of energy.
A general problem in the case of medical devices with insertable functional elements consists of the fact that a bodily fluid, such as e.g. blood or interstitial fluid, can emerge from the insertion site during or after the insertion, which insertion site is where the functional element or part thereof penetrates the body surface. This bodily fluid can contaminate the functional element and/or other components of the medical devices. Thus, by way of example, a bodily fluid may reach electrical contacts of a sensor element, which contacts are arranged within the control part, and may cause e.g. leakage currents or other electronic interference there.
U.S. Pat. No. 5,951,521 has disclosed an implantable subcutaneous set for assembly on a skin surface of a user. Here, a base with a cannula is used while a subcutaneous sensor is being inserted. The cannula has a lumen, within which the sensor is arranged. It is furthermore proposed to route a tube line into the interior of the cannula and into the lumen in order to suction off bodily fluid collecting in the lumen after the insertion. The tube line is provided with a connector that can for example be connected to a syringe.
U.S. Publication No. 2003/0004403 A1 has disclosed methods and devices for continuously monitoring physiologically relevant body states. Inter alia, it is proposed therein to use a so-called biointerface head (BIH), which is implanted into a body tissue. Inter alia, it is proposed, in the process, to embody the biointerface head with a hollow tube line, by means of which e.g. anti-inflammatory medicaments can be introduced into the body tissue or excessive bodily fluid can be routed out of the body tissue.
However, none of the above-described devices solves the sketched-out problem that bodily fluid emerging at the insertion site can contaminate the medical device. On the contrary, the tube connections revealed in the two aforementioned documents even lead to bodily fluid additionally being able to be guided out of the body of the user from the interior of the body tissue, which bodily fluid can contaminate the medical device outside of the body and which has to be separately disposed of there. Moreover, both documents describe a separate channel in conjunction with a sensor or a cannula, which channel requires additional space and hence makes an insertion of the sensor more difficult.